First Report of Human Infection with Avian Influenza without Confirmed Animal Contact in the United States

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AFP and other news agencies reported on the 7th (local time) that a human infection case of avian influenza (AI) was confirmed in the United States without any contact with infected animals.

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According to a statement released on the same day by the Centers for Disease Control and Prevention (CDC) and Missouri state health authorities, a patient who was hospitalized with flu symptoms in Missouri on the 22nd of last month was later found to be infected with the H5 subtype of avian influenza after virus testing.

The patient had underlying health conditions, received treatment at the hospital, recovered, and was discharged.

The CDC stated that no human-to-human transmission was confirmed among other people who had contact with this patient.

This is the 14th person in the United States to test positive for avian influenza this year.

However, AFP reported that this is the first time since the first human infection case of avian influenza was reported in the U.S. in 2022 that a person who is not involved in livestock farming has tested positive.

It is reported that the route of contact with other infected animals for this patient has not been identified.

Missouri health authorities said, "There have been no reported cases of H5 infection in mammals such as dairy cattle in Missouri," but added, "However, H5 infections have been reported in some commercial or backyard poultry and wild birds."

Maria Van Kerkhove, head of epidemic preparedness and prevention at the World Health Organization (WHO), told AFP, "It is important that investigations into this patient’s exposure (how the infection occurred) continue in order to identify future prevention and response measures."

Recently, outbreaks of highly pathogenic avian influenza such as H5N1 have been repeatedly found in mammalian groups including dairy cattle worldwide, including in the United States, raising concerns about human-to-human transmission.

Previously, the WHO expressed concern that if avian influenza begins to spread among mammalian groups, there is a high possibility of mutations enabling human-to-human transmission.

Rare cases have also been reported in some countries such as Mexico where people infected with avian influenza had no known exposure to poultry or other animals.

However, there is still no confirmed evidence that the virus infecting humans has been continuously transmitted to other people.